1. Field of the Invention
The present invention relates to an ion-measuring electrode device including a gelatinized member which can be used as internal solution in the electrode structure, as an element in the preservation of an electrode or as a reference for the calibration of a glass electrode. The gelatinized member can be used for either the measuring ion electrode or the reference electrode and the like (hereinafter called generally an electrode for measuring ions) particularly in the case where the electrode for measuring ions is constructed as a small-sized planar sheet that can be mounted on removable sample testing modules.
2. Description of the Prior Art
A prior art glass electrode for measuring ion concentrations, such as pH, pNa and the like, is shown in FIG. 1 and comprises a supporting cylinder or pipe "a" formed of an electrically insulating glass, an ion-response glass membrane "b" which is response to pH, pNa and the like having a semispherical shape formed at a pointed end of said supporting pipe "a" for example, by the balloon method so as to be adhered to the pointed end, an internal electrode "c" comprising for example an Ag wire, having a surface coated with AgCl and positioned in the supporting pipe "a" and an internal solution "d" comprising, for example, a 3.3M-aqueous solution of KCl supersaturated by AgCl with a phosphoric acid-buffer solution added and enclosed in said internal electrode "c". In addition, another prior reference electrode has a supporting cylinder or pipe "e" formed of an electrically insulating glass, a liquid junction member "f" formed of, for example, inorganic sintered porous substances, organic high molecular porous substances and the like impregnated with KCl positioned in a hole formed in a pointed end portion of the supporting pipe "e", an internal electrode "g" comprising an Ag wire having a surface coated with AgCl in the same manner as in the above described glass electrode, and also provided in the supporting pipe "e", and finally an internal solution "h" comprising, for example, a 3.3M-aqueous solution of KCl supersaturated by AgCl with a phosphoric acid-buffer solution added and enclosed in the internal electrode "g" as shown in FIG. 2. In referring to FIG. 2, "i" designates an internal solution-replenishing port having a cap "j" which is provided in the supporting pipe "e" so as to replenish any internal solution "h" that has been consumed.
These prior glass electrodes and reference electrodes have exhibited problems in that they are relatively large-sized and are difficult to mass-produce, so that not only are they remarkably expensive in the manufacture thereof but also they are not convenient in a measuring operation. Additionally, it is frequently necessary to preserve the glass electrode in pure water and the reference electrode in a 3.3M-aqueous solution of KCl, which is the same as the internal solution, even while they are not being used.
Furthermore, the calibration (for example, pH calibration) of a glass electrode is carried out by the use of a standard solution (in short, a phthalic acid-standard solution having a pH of 4, neutral phosphoric acid-standard solution having a pH of 7 and sodium borate-standard solution having a pH of 9), however, a relatively large amount of each standard solution is required and also a vessel (beaker and the like) for receiving the standard solution is required. In addition, if these standard solutions are left unattended in an opened condition, they are apt to change in concentration, deposit crystals and deteriorate, so that it is considerably difficult to preserve them in an excellent condition for a long time period. Accordingly, it is required to exchange the standard solutions at a relatively high frequency, so that they have been remarkably troublesome in use and also uneconomical.
A gelatinized salt solution for a reference electrode is disclosed in Japanese Patent Publication Open to Public Inspection No. Sho 47-7749. A compound electrode for use in the measurement of pH is disclosed in Japanese Patent Examined Publication No. Sho 47-45317. This electrode comprises an inside cylinder enclosing an internal electrode for use in the measurement and a gelatinized internal solution therein.
In a reference electrode as disclosed in Japanese Patent Publication Open to Public Inspection No. Sho 47-7749, an internal solution is gelatinized, so that the internal solution is not consumed from a liquid junction. However, merely a salt solution is gelatinized with a gelatinizer, so that a problem occurs in that a surface of the liquid junction becomes dried when the reference electrode is not used. Accordingly, it is necessary to cut off an end portion of the gelatinized internal solution together with a tube after each use of the reference electrode to renew the liquid junction. Japanese Patent Examined Publication No. Sho 47-45317 discloses an electrode having an internal solution comprising neutral phosphate and potassium chloride gelatinized with agar-agar or gelatine. However, since the internal solution disclosed in the above described, both Japanese Patents are prepared by merely gelatinizing the internal solution with a gelatinizer, problems occur in that when it is left unattended in air of normal temperature, it is dried, so that many problems occur in packing and preservation. Thus, the prior art is still seeking an improved compact ion concentration measuring apparatus.